At 9 p.m., the National Hurricane Center said the storm had sustained winds of 100 miles per hour and upgraded it to a Category 2 hurricane. North Carolina state officials said they were surprised that the storm had veered a little to the west and they began to prepare for it to pass over part of the Outer Banks on its way north toward Nova Scotia.

By 11:30, Hurricane Arthur had crossed over the strip of land just east of the town of Beaufort, making it the first hurricane to make landfall in the continental United States since 2012. By then, Hatteras Island had been evacuated, Gov. Pat McCrory had declared emergencies for 26 counties and curfews had been imposed in several communities.

“This is a serious storm,” Gov. McCrory said at a late evening briefing. He said the storm’s move toward land had raised the threat of flooding inland and he advised people near the edge of the storm’s path to stay indoors until daylight.

For much of the day Thursday along the coast, thousands of residents and visitors had mostly shrugged off the first named storm of the Atantic hurricane season. The sun was still shimmering when Bill Peters stared out of the Cypress House Inn and pronounced his property nearly ready for Hurricane Arthur. Most of the storm shutters were closed. He would soon be contacting scheduled guests to see whether they wanted to delay their arrivals by a day or two. And, scrawled in blue chalk outside the front door, someone had left a message: “Go away, Arthur!!!”

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Cheryl Blankenship with Boston, her 9-month-old son, in Nags Head, N.C., where the family was vacationing on Thursday. Hurricane Arthur is expected to pass over or near North Carolina on Friday, forcing thousands of people to abandon their Independence Day plans. The Blankenship family is hoping to ride out the storm.CreditLibby March for The New York Times

As Mr. Peters, who has run his inn here on the Outer Banks for a decade, prepared for the arrival of a surprisingly strong storm, some of his guests were still at the beach.

“My friends paid a lot of money for their vacation,” said Shane Sanner, 23, who was visiting from Pennsylvania with about a dozen others, as he arrived at Jennette’s Pier in nearby Nags Head with a fishing pole.

Although a waitress at a popular local restaurant laughed and shook her head when asked whether she knew anyone evacuating, a steady flow of automobiles headed inland on Thursday and only a few vehicles could be seen on the highway traveling to the coastline.

Ashley Scadding, who spent Thursday morning on the beach and decided in the afternoon to leave, said she and her husband chose to depart after meteorologists announced that the storm had strengthened. But she said they were not evacuating because they feared for their safety.

“To be honest, we weren’t sure about flooding for our car, and we need to be back for work and need the car to be back,” said Ms. Scadding, who had planned to stay until Saturday.

Emergency officials along the coast were preparing for the possibility of flooding and isolated tornadoes, and lifeguards placed yellow flags reading “dangerous current” on beaches by midday.

But for Cheryl Blankenship, who was holding her 9-month-old son at the edge of the Atlantic, Thursday was another day at the beach, even if the pleasantness of its early hours was a surprise.

“I thought that I wouldn’t get to come here today,” Ms. Blankenship said as she stood below a pier that Hurricane Isabel heavily damaged in 2003. “I thought the red flags would be flying and there would be sand blowing. But it’s beautiful now.”

Dan and Erica Robinson, who were passing through Kill Devil Hills on their honeymoon, actually intended to drive through the storm as they traveled toward South Carolina. They briefly considered retreating to Virginia before opting for what they said would be a bit of adventure.

“At the red light, we said, ‘Left or right?'” Ms. Robinson said. “And right took us south.”

Her husband added, “You don’t want to end up in a Category Five, but this is going to be wimpy.”

Others who considered leaving the Outer Banks chose to stay because, without an ordered evacuation, they were ineligible for refunds on their lodging.

Although plenty of vacationers were sticking with their plans, members of the hospitality industry were concerned about the loss of business on a weekend that is among the most lucrative of the year.

“It’s not a season-killer, but it’s a chunk of revenue that we won’t get back,” said Mr. Peters, who had cancellations.

Part of the problem for others whose livelihoods depend on tourism is that even if visitors stay on the Outer Banks for the storm, the damage could restrict their movements in the days ahead. In anticipation of that, many of those who chose to stay were preparing for extended power failures and had stockpiled food and entertainment.

“We’re hoping we don’t lose power,” said Thelma Skinner, a New Yorker visiting the coast. “We have puzzles and games, and if we lose power, I guess we’ll sleep.”

They had little choice but to stay, Ms. Skinner said, because of the limited prospects of securing inland hotel rooms for the 14 people in her traveling party.

“I think we’re just going to wing it and hope and pray we’re going to be O.K.,” she said.